1. Field of the Invention
The present invention relates to a circuit module. More particularly, the present invention relates to a circuit module including a case that is mounted so as to cover an electronic component mounted on a substrate.
2. Description of the Related Art
A circuit module of the related art includes a substrate, component lands provided on the substrate, an electronic component bonded to the component lands, case lands provided on the substrate, and a case bonded to the case lands so as to cover the electronic component.
In such a circuit module, the case is usually bonded to the case lands by heating and melting solder on the case lands in a reflow furnace. Therefore, when the width of the case lands is relatively large in order to provide a sufficient bonding strength of the case, the mounting position of the case is displaced. Accordingly, Japanese Unexamined Patent Application Publication No. 2004-186570 discloses a structure that attempts to prevent displacement of the mounting position of the case.
In the structure disclosed in Japanese Unexamined Patent Application Publication No. 2004-186570, as illustrated in FIG. 10, case lands 111 are provided on a substrate 110. The case lands 111 include narrow positioning portions 111a and wide bonding-strength securing portions 111b. When solder is melted by being heated in a reflow furnace, the case 112 is displaced. Japanese Unexamined Patent Application Publication No. 2004-186570 discloses that displacement of the case 112 can be prevented because the amount of displacement is dependent upon the narrow positioning portions 111a of the case lands 111.
In the above-described structure, the shape of the case lands on the substrate must be optimized in accordance with the size and shape of the case. For this reason, the design must be changed for each circuit module. Further, the amount of solder during mounting is less at the narrow portions of the case lands of the case than at the wide portions. Therefore, the bonding strength between the case and the substrate is decreased. In addition, since the area of the case lands must be increased in order to increase the bonding strength, the overall size of the circuit module is increased.